1. Field of the Invention
This invention relates to a sine generation circuit for obtaining a sin θ (sine-converted) output signal from an input signal (θ), specifically to a sine generation circuit comprising bipolar transistors. This invention also relates to a phase shift circuit used in a television set, specifically to a phase shift circuit comprising bipolar transistors. Additionally this invention relates to a tint adjustment circuit used in a television set, specifically to a tint adjustment circuit comprising the bipolar transistors.
2. Description of the Related Art
A viewer of a television, in general, makes a tint adjustment of a chrominance signal by using external adjusting means, such as a volume dial, of the television set. For adjusting the tint, a demodulation axis (x-axis, y-axis) of the chrominance signal should be rotated in both directions. To rotate the modulation axis, the phase of a color carrier of 3.58 MHz applied to a modulator should be changed.
FIG. 6 shows a tint adjustment circuit for changing the phase of the color carrier of 3.58 MHz. In FIG. 6, the color carrier is applied to an input terminal 1, and a horizontal synchronous pulse is applied to a terminal 2.
A burst separation circuit 3 extracts only a burst signal from the color carrier inputted from the input terminal 1 based on a horizontal synchronous pulse. The extracted burst signal is converted to a continuous wave of the burst by a continuous wave generation circuit 4 (CW generation circuit).
This continuous wave is applied to the demodulator 6 of the chrominance signal through a phase shift circuit 5. The demodulator 6 receives the chrominance signal from a terminal 7 and demodulates a B-Y color difference signal and an R-Y color difference signal to terminals 8 and 9. Two kinds of continuous waves are required to demodulate these two signals and the phase shift circuit 5 supplies two continuous waves used for the B-Y color difference signal and the R-Y color difference signal to the demodulator 6.
Therefore, when a viewer changes the amount of phase shift of the phase shift circuit 5 using the external adjusting means, the tint of the chrominance signal can be adjusted based on the principal described above.
However, in the above circuit configuration, although the phase control as described above can be performed to the signal going through the demodulator 6, phase control cannot be performed to the signal which does not go through the demodulator 6. That is, although the tint adjustment can be performed to the modulated chrominance signal, the tint adjustment can not be performed to the chrominance signal after the demodulation.
When a DVD player is connected to a television set, a component signal (Y, Cb, Cr) is applied to the television set from outside. The chrominance demodulation has already been performed to such a signal. Thus, the tint adjustment can not be performed with the conventional circuit described above.